The present invention relates to a composite structure including a carrier layer of aluminum having on the surface thereof a covering layer of copper which structure is characterized by the fact that the aluminum layer can be readily removed by mechanical means from the copper layer, and to the method of producing such a composite structure.
Articles of the invention find utility, in the main, in the printed circuit industry. In this use, the composite structure of the invention is bonded to an insulating substrate by laminating techniques. The aluminum carrier layer is then mechanically separated from the copper layer which has become bonded to the insulating substrate. The desired pattern is then formed in the copper layer.
While the above general technique is used extensively today in thin foil applications, it is not devoid of problems. For example, difficulties are often experienced in connection with the laminating procedure. To obtain good electrical, mechanical and chemical properties from the composite foil substrate, it is often necessary to use high temperatures (often in excess of 400.degree. F.) and pressures. While this technique also results in a good bond between the copper foil and the insulating substrate, it, unfortunately, reduces the strippability of the aluminum carrier layer. Obviously, this problem of reduced strippability is to be avoided, if possible.
Accordingly, it is the principal object of the present invention to provide a composite structure which includes a carrier layer of aluminum and a covering layer of copper which structure can be readily bonded to an insulating substrate by high temperature laminating techniques and is characterized by the fact that the carrier layer of aluminum can be readily separated from the copper layer by simple mechanical means after the laminating procedure.
Another object of the present invention is to provide a composite structure consisting of a carrier layer of aluminum and a covering layer of copper which is characterized by the fact that the copper layer is tenaciously bonded to the carrier layer but readily separable therefrom by mechanical means.
Other objects of the invention will become apparent from a reading of the following description and claims.